Fluororubber composition and molded article thereof

ABSTRACT

A fluororubber composition comprising a fluororubber, a vulcanizing agent and 0.1 to 5 wt. parts of a fatty acid monoamide per 100 wt. parts of said fluororubber. This fluororubber composition is excellent in mold releasability, and a molded article obtained by vulcanizing and molding the composition suffers less deterioration of mechanical properties caused by the addition of an internal mold release agent.

FIELD OF THE INVENTION

The present invention relates to a fluororubber composition and a moldedarticle of a fluororubber. In particular, the present invention relatesto a fluororubber composition which is excellent in mold releasabilityin a vulcanizing molding step, and a molded article produced byvulcanizing said composition.

PRIOR ART

Examples of the conventional molding methods of a rubber are molding ina mold using a compression molding press (heat press), extrusion moldingwith an extruder, and so on. In the compression molding, a suitable moldrelease agent should be selected and used.

In general, in the case of the fluororubber, an external mold releaseagent which is coated on the mold such as a silicone emulsion type oneor fluorine containing one is used. But, the external mold release agentshould be applied on the mold surface before every shot, and may causemold contamination. A contemplated solution for such problems is aninternal mold release agent. However, the internal mold release agentcannot solve the problem of mold contamination satisfactorily. Inaddition, the internal mold release agent has drawbacks that it oftencauses fusing failure, deterioration of physical properties of themolded article, etc. For example, JP-A-2-281062 discloses compounding ofa mixture of a metal salt of an aliphatic carboxylic acid and analiphatic bisamide or a N-substituted aliphatic amide in a fluororubber.When such internal mold release agent is used, some problems arise, thatis, a mold releasability is insufficient, the physical properties of themolded article are deteriorated greatly, and so on.

Further, the conventional internal mold release agent has a drawbackthat a "thin burr" adheres to the molded article so that defectivemolded articles are produced. That is, when the molded article of thefluororubber is produced by the compression molding or extrusionmolding, an unnecessary part which is called as a "thin burr" remains onthe molded article. Since the "thin burr" has tackiness, it bends andadheres to the molded article and its removal is difficult. Then, themolded article having the adhered thin burr is subjected to secondaryvulcanization, whereby the product is defective.

SUMMARY OF THE INVENTION

Objects of the present invention are to provide a fluororubber which isexcellent in mold releasability, does not deteriorate properties, inparticular, compression set of a molded article thereof, and makes a"thin burr" non-tacky, and also to provide a molded article of afluororubber having excellent properties.

As a result of the extensive study to solve the above problems, it hasbeen found that when the fluororubber containing a fatty acid monoamideis vulcanized and molded, the above problems can be solved, and then thepresent invention has been completed.

According to one aspect of the present invention, there is provided afluororubber composition comprising a fluororubber, a vulcanizing agentand 0.1 to 5 wt. parts of a fatty acid monoamide per 100 wt. parts ofsaid fluororubber.

According to another aspect of the present invention, there is provideda fluororubber composition comprising 100 wt. parts of a fluororubber,0.1 to 5 wt. parts of a fatty acid monoamide and 0.1 to 5 wt. parts of afluorine-containing surfactant.

According to a further aspect of the present invention, there isprovided a molded article of a fluororubber which is obtained byvulcanizing and molding the above composition.

DETAILED DESCRIPTION OF THE INVENTION

Herein, the fluororubber means a fluorinated elastomeric polymer, andincludes all of the known fluororubbers. Typical examples of thefluororubber are vinylidene fluoride/hexafluoropropene base rubber(preferred molar ratio of vinylidene fluoride/hexafluoropropene being45-95:55-5), vinylidene fluoride/ tetrafluoroethylene/hexafluoropropenebase rubber (preferred molar ratio of vinylidenefluoride/tetrafluoroethylene/hexafluoropropene being 45-90:1-35:5-50),vinylidene fluoride/chlorotrifluoroethylene base rubber,tetrafluoroethylene/propene base rubber, hexafluoropropene/ethylene baserubber, perfluoro(alkyl vinyl ether) (which may have plural etherbonds)/olefin (e.g. tetrafluoroethylene, ethylene, etc.) base rubber(preferred molar ratio of perfluoro(alkyl vinyl ether)/olefin being15-75:85-25), fluorosilcone rubber, fluorophosphazene rubber, and so on.Preferred fluororubber is a copolymer comprising vinylidene fluoridemonomer and at least one other monomer and containing 80 wt. % or lessof vinylidene fluoride monomeric units. The fluororubber may be onecomprising an iodine or bromine atom bonded to a polymer chain toincrease a crosslinking reactivity (see JP-A-53-125491, JP-B-53-4115 andJP-A-59-20310).

Preferably, the fluororubber has a molecular weight of 3000 to 1,200,000(measured by a gel permeation method).

Preferably, the fatty acid monoamide which is used to achieve theobjects of the present invention is an unsaturated or saturated fattyacid monoamide having at least 12 carbon atoms, more preferably 12 to 24carbon atoms. A fatty acid monoamide having 11 or less carbon atoms isless preferred since it has odor (unpleasant odor). A fatty acidmonoamide having more than 24 carbon atoms is difficult to produce.

The saturated fatty acid monoamide is represented by the generalformula:

    C.sub.n H.sub.2n+1 CONH.sub.2

wherein n is an integer of 11 to 23. Preferred examples thereof arelauric acid amide, palmitic acid amide, stearic acid amide, behenic acidamide, and so on.

The unsaturated fatty acid monoamide is represented by the generalformula:

    C.sub.n H.sub.2n-1 CONH.sub.2

wherein n is an integer of 11 to 23. Preferred examples thereof areoleic acid amide, erucic acid amide, ricinoleic acid amide, and so on.

The fatty acid amide which is used to achieve the objects of the presentinvention may be any of the saturated and unsaturated ones as describedabove. In particular, the unsaturated fatty acid monoamide having 18 to24 carbon atoms is preferred, since it is excellent in moldreleasability.

The fatty acid monoamides may be used in admixture of two or more ofthem.

The fatty acid monoamide to be used in the composition of the presentinvention is used in an amount of 0.1 to 5 wt. parts, preferably 0.2 to2 wt. parts per 100 wt. parts of the fluororubber. When the amount ofthe monoamide is less than 0..1 wt. part, the mold releasing effect isnot achieved, while when it exceeds 5 wt. parts, the properties of themolded article are deteriorated and also the defective molding occurs.

To improve the mold releasability, a fluorine-containing surfactant maybe added to the composition of the present invention. In the case of thecomposition of the present invention, the use of the fluorine-containingsurfactant can make the thin burr non-tacky and increase the effect ofpreventing the mold contamination when the mold is used for a long time.Preferred fluorine-containing surfactants are those described inJP-B-1-16431 (the compounds described from column 4, line 14 to column17, line 34 of the Publication). Specific examples are compounds of theformulas: ##STR1## wherein Rf is a fluoroalkyl group having 3 to 21carbon atoms.

The fluorine-containing surfactant is used in an amount of 0 to 5 wt.parts, preferably 0.1 to 2 wt. parts per 100 wt. parts of thefluororubber.

The composition of the present invention may contain any of variousadditives which are used with conventional rubbers.

For example, as auxiliary fillers, there are used metal oxides (e.g.calcium oxide, titanium oxide, silicon oxide, zinc oxide, lead oxide,aluminum oxide, etc.), metal hydroxides (e.g. magnesium hydroxide,aluminum hydroxide, calcium hydroxide, zinc hydroxide, lead hydroxideetc.), carbonates (e.g. magnesium carbonate, aluminum carbonate, calciumcarbonate, barium carbonate, etc.), silicates (e.g. magnesium silicate,calcium silicate, sodium silicate, aluminum silicate, etc.), sulfates(e.g. aluminum sulfate, calcium sulfate, barium sulfate, etc.), sulfides(e.g. molybdenum sulfide, ion sulfide, copper sulfide, etc.),diatomaceous earth, asbestos, lithopone (zinc sulfide/barium sulfate),graphite, carbon black, carbon fluoride, calcium fluoride, cokes,wollastonite, mica powder, glass powder, carbon fiber, quartz powder,and so on. These fillers may be used in combination of two or more ofthem.

An amount of the auxiliary filler is from 0 to 100 wt. parts, preferablyfrom 0 to 50 wt. parts.

In addition, a colorant, a flame retardant, a stabilizer, a plasticizer,an oil-resistance improver, a scorch retarder, and so on may be addeddepending on the purposes.

As a vulcanizing manner, there are exemplified peroxide vulcanizationusing an organic peroxide, polyol vulcanization using a polyhydroxycompound, polyamine vulcanization using a polyamine compound, andpolythiol vulcanization using a polythiol compound. Any one of thesemanners can be used in the present invention. Among them, the polyolvulcanization using the polyhydroxy compound is preferred.

A vulcanizing agent is used in an amount of 0.05 to 10 wt. parts,preferably 0.5 to 5 wt. parts per 100 wt. parts of the fluororubber.

As the organic peroxide compound, a compound which readily generates aperoxide radical by heating or in the presence of a redox system ispreferred. Examples of the organic peroxide compound are1,1-bis(tert.-butylperoxy)-3,5,5-trimethylcyclohexane,2,5-dimethyl-2,5-dihydroxyperoxide, di-tert.-butylperoxide,tert.-butylcumylperoxide, dicumylperoxide,α,α-bis(tert.-butylperoxy)-p-diisopropylbenzene,2,5-dimethyl-2,5-di(tert.-butylperoxy)hexane,2,5-dimethyl-2,5-di(tert.-butylperoxy)hexane3, benzoylperoxide,tert.-butylperoxybenzene, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane,tert.-butylperoxymaleic acid, tert.-butyl-peroxyisopropyl carbonate, andso on. Among them, the dialkyl type compounds are preferred. A kind andamount of the organic peroxide compound are selected according to anamount of active --O--O--groups, a decomposition temperature, etc.

When the organic peroxide compound is used, combined use of acrosslinking aid or co-crosslinking agent improves the effect of theperoxide compound greatly. Any crosslinking aid or co-crosslinking agentmay be effective insofar as it has a reactivity with a peroxy radicaland a monomer radical, and its kind is not limited. Preferred examplesof the crosslinking aid or co-crosslinking agent are triallyl cyanurate,triallyl isocyanurate, triacryl formal, triallyl trimellitate,N,N'-m-phenylene bismaleimide, dipropargyl terephthalate, diallylphthalate, tetraallyl terephthalamide, and vinyl group-containingsiloxane oligomers such as polydimethylvinylsiloxane andpolymethylphenylvinyl siloxane, etc. An amount of the crosslinking aidor co-crosslinking agent to be used is from 0.1 to 10 wt. parts,preferably 0.5 to 5 wt. parts per 100 wt. parts of the fluororubber.

As a polymer to be blend crosslinked with the fluororubber, there areused polymers which can be crosslinked with the peroxide such assilicone oil, silicone rubber, ethylene/vinyl acetate copolymer,1,2-polybutadiene, fluorosilicone oil, fluorosilicone rubber,fluorophosphazene rubber, hexafluoropropylene/ethylene copolymer,tetrafluoroethylene/propylene copolymer, epichlorohydrin rubberincluding copolymers, urethane rubber, halogenated butyl rubber,nitrile-butadiene rubber, and the like.

An amount of the crosslinkable polymer is not limited, but should not belarge enough to deteriorate the properties of the fluororubber.

As the polyhydroxy compound, there are used a polyhydroxy compoundhaving a phenolic hydroxyl group: ##STR2## a dihydroxy compound of theformula:

    Rf(CH.sub.2 OH).sub.2

wherein Rf is a polyfluoroalkylene or perchlorofluoroalkylene grouphaving 1 to 20 carbon atoms, their alkali metal salts, and mixturesthereof.

Preferred examples of such polyhydroxy compound are hydroquinone,2,2-bis(4-hydroxyphenyl)propane,2,2-bis(4-hydroxyphenyl)perfluoropropane,2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)methane,4,4-dihydroxydiphenyl ether, HOCH₂ (CF₂)₂ CH₂ OH, HOCH₂ CF₂ CFH(CF₂)₂CFHCF₂ CH₂ OH, HOCH₂ CH₂ CH ₂ (CF₂)₃ CH₂ CH₂ CH₂ OH, HOCH₂ CF₂ CH₂(CF₂)₃ CH₂ CF₂ CH₂ OH, and their alkali metal salts.

The polyamine compound may be a primary or secondary amine having atleast two basic nitrogen atoms in a molecule. In many cases, it is usedin a salt form which has a milder reactivity. Specific examples of thepolyamine compound are alkylenediamines. Among them, ethylenediaminecarbamate, hexamethylenediamine carbamate, 4,4'-diaminecyclohexylmethanecarbamate, and so on are frequently used. A Schiff base such asN,N'-dicinnamylidene-1,6-hexamethylenediamine is often used also.Further, an aromatic polyamine compound which is less basic can bepreferably used when it is used in combination with other basiccompound. Examples of the other basic compound are diphenylguanidine,di-O-triguanidine, diphenylthiourea, 2-mercaptoimidazoline, a compoundhaving a --HN₂ and/or --NH group in a molecule which is used as anaccelerator for a synthetic rubber, and divalent metal hydroxides.

Examples of the polythiol compound are dimercaptodimethyl ether,dimercaptomethylsulfide, 1,6-hexanedithiol, ethylenebismercaptoacetate,1,5-naphthalene dithiol, 4,4'-dimercaptodiphenyl, 2-substituted(anilino-, dibutylamino-, etc.)-4,6-dithiol-S-triazine, and their alkalimetal salts.

Further, as a vulcanizing accelerator, there may be optionally used atertiary amine, a tri-substituted amidine, a penta-substituted guanidineor their salt with an organic or inorganic acid, a quaternary ammoniumsalt, a quaternary phosphonium salt or a nitrogen-containing cyclicpolyether. These crosslinking accelerators are described inJP-A-51-56854, JP-A-47-1387, JP-A-47-191, and JP-A-53-132858.

To compound the above components, a conventional open roll mill is usedgenerally.

The fluororubber composition of the present invention can be vulcanizedunder vulcanizing conditions employed for vulcanizing a conventionalfluororubber. For example, after milling the fluororubber composition, amass of the composition is placed in a mold and heated at a temperatureof 150° to 200° C., under pressure of 3 to 100 kg/cm² G, in general 3 to30 kg/cm² G for 3 to 60 minutes to effect press vulcanization and then,if necessary, maintained in an oven at a temperature of 180° to 260° C.for 0 to 24 hours to effect oven vulcanization, whereby the moldedarticle is obtained.

The molded article of the present invention is useful as an O-ring, apacking, an automobile part, a general industrial part, and so on.

The present invention will be illustrated by the following Examples,which do not limit the scope of the present invention.

EXAMPLES Examples 1-2 and Comparative Examples 1-8

A vinylidene fluoride (VdF)/hexafluoropropylene (HFP) copolymer (a molarratio of VdF to HFP=78:22. Mooney viscosity ML₁₊₁₀ (100° C.)=65) (100wt. parts), bisphenol AF as a polyol vulcanizing agent (1.5 wt. parts),8-benzyl-1,8-diazabicyclo- 5.4.0!undecenium chloride (DBU-B) as avulcanizing accelerator (0.3 wt. part), carbon black N-990 (manufacturedby CANCARB) (20 wt. parts), magnesium oxide (KYOWAMAG MA-150manufactured by KYOWA Chemical Industries, Ltd.) (3 wt. parts), calciumhydroxide (CALDIC-2000 manufactured by OHMI Chemical Industries, Ltd.)(6 wt. parts) and one of mold release agents, namely, oleic acid amide(Example 1), stearic acid amide (Example 2), stearic acid (ComparativeExample 2), sodium stearate (Comparative Example 3), zinc stearate(Comparative Example 4), myristic acid (Comparative Example 5),stearylamine (Comparative Example 6), stearyl isocyanurate (ComparativeExample 7) or oleylamine (Comparative Example 8) (1 wt. part) were mixedand milled on an open roll mill at a room temperature for 30 minutes toobtain a composition for vulcanization. A composition containing thesame components with no mold release agent was prepared (ComparativeExample 1).

Then, using a hard chromium plated mold, a mass of each composition waspress vulcanized under a pressing pressure of 30 tons, at a pressingtemperature of 185° C. for 3 minutes to mold P-8 O-rings. The mold wasfor molding 65 pieces of P-8 O-rings.

After press vulcanization, the O-rings were peeled off from the mold byhands. Then, the number of O-rings which remained on the mold werecounted and their percentage (%) per the whole number of the O-rings wasused to evaluate the releasability of the composition from the mold.Then, the smaller remaining percentage means better mold releasability.

With the molded article, its tensile strength, elongation and hardnesswere measured according to JIS K 6301.

A compression set of the molded article was measured as follows:

An O-ring (an inner diameter of 23.7 mm, a wall diameter of 3.5 mm) washeated at 200° C. for 70 hours with pressing it by 25 %. Thereafter, thecompression set was measured by the method B of ASTM D-396-61.

The results are shown in Table 1.

                  TABLE 1    ______________________________________                     Mold                     re-    Properties of molded article                     leas-  (original state)                     abil-  Tensile                                   Elon- Hard- Com-         Mold        ity    strength                                   gation                                         ness  pression         release agent.sup.a)                     (%)    (kgf/cm.sup.2)                                   (%)   (JIS A)                                               set (%)    ______________________________________    Ex. 1         Oleic acid amide                     0      176    260   70    33    Ex. 2         Stearic acid                     7      170    260   70    33         amide    C.   --          37     180    310   68    27    Ex. 1    C.   Stearic acid                     54     183    260   71    39    Ex. 2    C.   Sodium stearate                     25     149    220   72    40    Ex. 3    C.   Zinc stearate                     72     171    260   72    39    Ex. 4    C.   Myristic acid                     51     170    260   71    38    Ex. 5    C.   stearylamine                     29     175    230   72    44    Ex. 6    C.   Stearyl     2      186    250   69    43    Ex. 7         isocyanurate    C.   Oleylamine  37     180    230   72    47    Ex. 8    ______________________________________     Note:     .sup.a) An amount was 1 wt. part per 100 wt. parts of the fluororubber.

Examples 3-9 and Comparative Examples 9-18

The vinylidene fluoride/hexafluoropropene copolymer used in Example 1(100 wt. parts), bisphenol AF as a polyol vulcanizing agent (2 wt.parts), 8-benzyl-1,8-diazabicyclo- 5.4.0!undecenium chloride (DBU-B) asa vulcanizing accelerator (0.35 wt. part), carbon black N-990(manufactured by CANCARB) (20 wt. parts), magnesium oxide (KYOWAMAGMA-150 manufactured by KYOWA Chemical Industries, Ltd.) (3 wt. parts),calcium hydroxide (CALDIC-2000 manufactured by OHMI Chemical Industries,Ltd.) (6 wt. parts) and erucic acid amide in an amount of 1 wt. part(Example 3), 0.75 wt. part (Example 4), 0.5 wt. part (Example 5), 0.45wt. part (Example 6) or 0.25 wt. part (Example 7) were mixed and milledon an open roll mill at a room temperature for 30 minutes to obtain acomposition for vulcanization. In the same manner as above but using, asa mold release agent, 1 wt. part of behehic acid amide (Example 8),lauric acid amide (Example 9), carnauba wax (Comparative Example 10),rice bran wax (Comparative Example 11), shellac wax (Comparative Example12), N-oleyloleic acid amide (Comparative Example 13), N-stearyloleicacid amide (Comparative Example 15), N-stearyl-N'-stearylurea(Comparative Example 16), N-butyl-N'-stearylurea (Comparative Example17) or N-phenyl-N'-stearylurea (Comparative Example 18) in place oferucic acid amide, or no mold release agent (Comparative Example 9), acomposition for vulcanization was prepared.

Then, in the same manner as in Example 1, the composition was pressvulcanized to obtain O-rings.

Mold releasability in the press molding, and properties of the moldedarticle were evaluated in the same manners as in Example 1. The resultsare shown in Table 2.

                  TABLE 2    ______________________________________                        Mold   Properties of molded article                        re-    (original state)                        leas-  Tensile                                     Elon-                                          Hard-                        a-     strength                                     ga-  ness Com-          Mold release agent.sup.a)                        bility (kgf/ tion (JIS pression          (wt. part)    (%)    cm.sup.2)                                     (%)  A)   set (%)    ______________________________________    Ex. 3 Erucic acid amide (1)                        0      176   220  71   21    Ex. 4 Erucic acid amide                        0      170   210  71   21          (0.75)    Ex. 5 Erucic acid amide                        3      172   210  71   20          (0.5)    Ex. 6 Erucic acid amide                        3      175   200  70   20          (0.45)    Ex. 7 Erucic acid amide                        10     168   200  70   20          (0.25)    Ex. 8 Behenic acid amide (1)                        8      173   200  71   21    Ex. 9 Lauric acid amide (1)                        6      178   190  70   20    C.    --            28     160   210  70   20    Ex. 9    C.    Carnauba wax (1)                        29     176   190  71   32    Ex. 10    C.    Rice bran wax (1)                        34     166   200  70   31    Ex. 11    C.    Shellac wax (1)                        12     167   190  71   30    Ex. 12    C.    N-Oleyloleic acid                        54     172   200  70   27    Ex. 13          amide (1)    C.    N-Stearyloleic acid                        48     169   200  71   26    Ex. 14          amide (1)    C.    N-Oleylstearic acid                        54     155   190  71   25    Ex. 15          amide (1)    C.    N-Stearyl-N'-stearyl-                        54     162   190  71   30    Ex. 16          urea (1)    C.    N-Butyl-N'-stearyl-                        34     169   190  72   27    Ex. 17          urea (1)    C.    N-Phenyl-N'-stearyl-                        46     171   180  72   28    Ex. 18          urea (1)    ______________________________________

From the results shown in Table 1 and 2, it is seen that oleic acidamide and erucic acid amide used according to the present invention havethe excellent mold releasability.

The compression set is minimum when no mold release agent is used, andtends to increase when the mold release agent is added.

A tolerance limit of the increase of the mold compression set is 30% orless in comparison with the composition containing no mold releaseagent. The molded articles according to the present invention have thecompression set within this tolerance limit.

Examples 10-11 and Comparative Example 19

To the composition of Example 5, the following fluorine-containingsurfactant was added in an amount of 0.5 wt. part per 100 wt. parts ofthe fluororubber (Example 10).

Separately, a composition for vulcanization was prepared from thecomposition of Example 5 in the same manner as above but using 0.25 wt.part of erucic acid amide and 0.25 wt. % of the fluorine-containingsurfactant (Example 11).

Properties of the compositions were evaluated in the same manners as inExample 1, and also a degree of mold contamination was evaluated usingthe same mold and press molding conditions.

The used fluorine-containing surfactant had the following structure:##STR3##

When the mold surface was not contaminated after 200 times molding, thecomposition was ranked "Excellent". When the mold surface was slightlyclouded after 100 times molding, it was ranked "Good". When the moldsurface was severely clouded after 100 times molding, it was ranked"Bad".

The results are shown in Table 3.

For comparison, the same composition as that of Example 10 except thatno erucic acid amide was added was prepared in Comparative Example 19.The results are also shown in Table 3.

In addition, with the compositions of Example 5 and Comparative Example9, the mold contamination was evaluated. The results are shown in Table3.

                                      TABLE 3    __________________________________________________________________________                             Properties of molded article                             (original state)    Mold        Mold         Tensile        Compression    release agent.sup.a)                releasability                      Mold   strength                                  Elongation                                       Hardness                                            set    (wt. part)  (%)   contamination                             (kgf/cm.sup.2)                                  (%)  (JIS A)                                            (%)    __________________________________________________________________________    C. Ex. 9         --     28    Good   160  210  70   20    Ex. 1         Erucic acid                 3    Good   172  210  71   20         amide (0.5)    C. Ex. 19         F-cont.                15    Excellent                             175  210  71   20         surfactant*         (0.5)    Ex. 10         Erucic acid                 0    Excellent                             171  210  71   21         amide (0.5)         F-cont.         surfactant*         (0.5)    Ex. 11         Erucic acid                 3    Excellent                             173  210  71   20         amide (0.25)         F-cont.         surfactant*         (0.25)    __________________________________________________________________________     Note:     *Fluorinecontaining surfactant:     ##STR4##

As described above, the composition of the present invention isexcellent in mold releasability, and the molded article obtained fromthe composition has less compression set than one obtained from afluororubber composition comprising a conventional internal mold releaseagent. Further, the "thin burr" of the molded article is made non-tacky.In addition, the molded article can be adhered by vulcanization.

What is claimed is:
 1. A fluororubber composition comprising afluororubber, which is vinylidene fluoride/hexafluoropropene vinylidenefluoride/tetrafluoroethylene/hexafluoropropene, vinylidenefluoride/chlorotrifluoroethylene, tetrafluoroethylene/propene,hexafluoropropene/ethylene or perfluoro (alkyl vinyl ether)/olefin, avulcanizing agent and 0.1 to 5 wt. parts of a fatty acid monoamide per100 wt. parts of said fluororubber.
 2. The fluororubber compositionaccording to claim 1, wherein said fatty acid monoamide is anunsaturated fatty acid monoamide.
 3. The fluororubber compositionaccording to claim 2, wherein said unsaturated fatty acid monoamide is acompound represented by the general formula:

    C.sub.n H.sub.2n-1 CONH.sub.2

wherein n is an integer of 11 to
 23. 4. The fluororubber compositionaccording to claim 2, wherein said unsaturated fatty acid monoamide is acompound represented by the general formula:

    C.sub.n H.sub.2n-1 CONH.sub.2

wherein n is an integer of 17 to
 23. 5. The fluororubber compositionaccording to claim 2, wherein said unsaturated fatty acid monoamide isat least one compound selected from the group consisting of oleic acidamide, erucic acid amide and ricinoleic acid amide.
 6. The fluororubbercomposition according to claim 1, wherein said fatty acid monoamide is asaturated fatty acid monoamide.
 7. The fluororubber compositionaccording to claim 6, wherein said saturated fatty acid monoamide is acompound represented by the general formula:

    C.sub.n H.sub.2n+1 CONH.sub.2

wherein n is an integer of 11 to
 23. 8. The fluororubber compositionaccording to claim 6, wherein said saturated fatty acid monoamide is atleast one compound selected from the group consisting of lauric acidamide, palmitic acid amide, stearic acid amide and behenic acid a amide.9. The fluororubber composition according to claim 6, wherein saidsaturated fatty acid monoamide is a mixture of a saturated fatty acidmonoamide and an unsaturated fatty acid monoamide.
 10. The fluororubbercomposition according to claim 1, wherein an amount of said vulcanizingagent is from 0.05 to 10 wt. parts per 100 wt. parts of saidfluororubber.
 11. The fluororubber composition according to claim 1,wherein said vulcanizing agent is selected from the group consisting oforganic peroxides, polyhydroxy compounds, polyamine compounds andpolythiol compounds.
 12. The fluororubber composition according to claim11, wherein said vulcanizing agent is a polyhydroxy compound.
 13. Thefluororubber composition according to claim 1, which further comprises0.1 to 5 wt. parts of a fluorine-containing surfactant per 100 wt. partsof said fluororubber.
 14. A molded article obtained by vulcanizing andmolding the composition claimed in claim 1.